[bitfolk] I've broken my Debian Jessie package update / upgrade system

Hi all, I would be very grateful if any Debian expert out there could offer me some advice. Somehow, probably editing my sources.list(s) in response to the recent jessie updates removal, I have managed to break the apt update/upgrade process: :~# apt-get upgrade Reading package lists... Done Building dependency tree Reading state information... Done You might want to run 'apt-get -f install' to correct these. The following packages have unmet dependencies: systemd : Depends: udev (>= 208-8) but it is not installed Recommends: libpam-systemd but it is not installed E: Unmet dependencies. Try using -f. After searching I've tried various suggested fixes such as apt-get -f install apt-get clean apt-get autoclean apt-get autoremove apt-get dist-upgrade dpkg --configure -a and so on but all to no avail. There is some info on my system below. Thanks in advance, Richard. ------------------------------ :~# uname -a Linux rglynsvr 3.16.0-7-686-pae #1 SMP Debian 3.16.59-1 (2018-10-03) i686 GNU/Linux ------------------------------- :~# systemd --version systemd 215 +PAM +AUDIT +SELINUX +IMA +SYSVINIT +LIBCRYPTSETUP +GCRYPT +ACL +XZ -SECCOMP -APPARMOR ------------------------------- ~# apt list --upgradable Listing... Done libsystemd0/jessie-backports 230-7~bpo8+2 i386 [upgradable from: 215-17+deb8u12] libudev1/jessie-backports 230-7~bpo8+2 i386 [upgradable from: 215-17+deb8u12] systemd/jessie-backports 230-7~bpo8+2 i386 [upgradable from: 215-17+deb8u12] -------------------------------- My /etc/apt/sources.list deb http://apt-cacher.lon.bitfolk.com/debian/ftp.uk.debian.org/debian/ jessie main contrib deb-src http://apt-cacher.lon.bitfolk.com/debian/ftp.uk.debian.org/debian/ jessie main contrib #deb http://apt-cacher.lon.bitfolk.com/debian/archive.debian.org/debian/ jessie-backports main contr$ #deb http://apt-cacher.lon.bitfolk.com/debian/security.debian.org/debian jessie/updates main contrib ------------------------------------- In sources.list.d/ there is certbot.list deb http://apt-cacher.lon.bitfolk.com/debian/archive.debian.org/debian/ jessie-backports main